A substantial part of a towed vehicle's weight is transmitted directly to the towing vehicle through the interconnecting hitch point. The hitch point is usually located at the rearward end of the towing vehicle, substantially rearward of the rear wheels. If the "tongue weight" of the towed vehicle is substantial, considerable control of the towing vehicle is lost and handling characteristics are adversely effected.
In response to the above problem and other inconveniences caused by standard hitch arrangements, "fifth wheel" connections have been developed. The typical fifth wheel arrangement involves the use of a specially constructed trailer having an overhang at the front end that will at least partially overlap the bed of a towing truck. The "fifth wheel" is a hitch connection attached to the truck bed just over the rear axle. Obviously, standard "blunt nose" trailers cannot make use of the "fifth wheel" since the trailer design will not allow such mounting. Furthermore, "fifth wheel" arrangements have, to this date, been typically used with pickups and trucks since there is no appropriate area for mounting over the rear differential of an automobile.
An advantage of a "fifth wheel" trailer connection is better handling characteristics due to the more direct transfer of "tongue weight" onto the rear axle of the towing vehicle. It remains desirable, however, to incorporate the fifth wheel advantages to standard trailers and forms of towing vehicles other than trucks and pickups.
U.S. Pat. No. 3,556,558 to McKee discloses a hitch arrangement by which the ordinary ball hitch of a trailer is connected to a drawbar. The drawbar, in turn, is pivotally connected to the vehicle frame adjacent the rear axle. An initial pivot is established directly behind the rear axle of the towing vehicle. This pivot point is maintained until the drawbar comes into abutment with the frame sides or some other abutment surface. At this time, "stabilizer bars" on the drawbar snap from engagement within a slot provided on a bracket fixed to the trailer tongue frame. The rods slide over the bracket to allow pivotal motion of the trailer and drawbar about the usual pivot axis at the ball hitch. Pivotal motion is also allowed at this time about the axis at the forward drawbar end, until the spring bars snap back into engagement with the notched bracket.
The vehicle operator must therefore contend with two simultaneously functional pivot points between the towing vehicle and trailer when maneuvering at sharp angles. The primary pivot at the forward end of the drawbar is limited in its pivotal motion only by abutment surfaces at the ends of a wide arc. The drawbar will pivot continuously within this arc depending only upon the angular orientation of the trailer to the towing vehicle. Also, once the "stabilizer bars" snap from engagement with the slotted bracket, both pivots become operable throughout the angular range dictated only by stops at the ends of prescribed angular motion.
Another attempted solution to this problem is exhibited by the "Miracle Hitch" product from "The Pullright Trailer Towing System" at 1612 W. Indiana Ave., Elkhart, Ind. 46514. The "Miracle Hitch" trailer hitch provides the advantages of a "fifth wheel" without regard to the type of towing vehicle. Like the McKee device, the "Miracle Hitch" mounts to the vehicle undercarriage to provide a primary hitch pivot near the towing vehicle rear axle. Unlike the McKee hitch, however, the "Miracle Hitch" is rigidly affixed to the tongue of the trailer vehicle and permits pivotal motion only at the forward end of the drawbar. This device therefore eliminates the possibility of simultaneous pivotal motion about two longitudinally separated axes and therefore demonstrates consistent maneuvering traits.
The problem remains, however, of providing maximum maneuverability afforded by a rearward hitch, while retaining control and favorable handling characteristics afforded by a "5th wheel" type hitch while the trailer is in transit. No previous hitch arrangement provides these combined abilities with a reasonable degree of safety and reliability.